Could not agree with NH-Couple more! In really was even better in the rain!!
We were there in mid-November and hiked during a morning of moderate-light but continuous rain but it did not detract from the experience at all, in fact once I'd given up on my rain-mac (it's still warm and I didn't like sweating underneath it) I thoroughly enjoyed getting soaked through. The trail was empty when we went (by one guided middle-aged couple [NH-Couple?!]) which made it even more special. We had been on 2-3 guided hikes already in Monteverde and Arenal so went without here, only paying the $10 park fee, which worked fine for us having driven there in our rented 4x4 (NB: do not try to drive to this trail without a 4x4, the roads are very rough and rocky and you have to ford a small stream).
The hike is not strenuous at all but very pleasant, the plank crossings are rudimentary but fun and have been wrapped in chicken-wire which delivered more than enough grip for us in our hiking boats.
Costa Rica is not suffocated by health & safety regulations, this is a wonderful relief compared to places like the UK and US - so stop complaining and enjoy it!!
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.